Automatic edger set works method and apparatus

ABSTRACT

Method and apparatus for scanning lumber, particularly cants, for determining the configuration thereof includes first and second light sources for directing beams of light at a low angle of incidence across the cant. The light reflected from the cant at a plurality of locations provides information on the amount and orientation of useable wood within the cant. This information may be used to orient the cant prior to sawing into studs. By proper orientation and positioning of the cant relative to the saws, maximum yield from each cant may be realized.

O Umted States Patent 1 1 1111 3,890,509 Maxey June 17, 1975 [54] AUTOMATIC EDGER SET WORKS 3,565,236 2/l97l Southworth 250/223 M H AND APPARATUS 3,62l,266 ll/l97l Akuta 3,648,743 3/!972 Finch. [75] Inventor: Carl W. Maxey, Everett, Wash. 3,73 9 3 6/1973 Mason. Assigneez The Black Clawson p y, 3,806,253 4/1974 Demon 144/312 H 'lt Oh on Io Primary Examiner-James W. Lawrence [2 Flledi 1974 Assistant ExaminerD. C. Nelms [211 App]. No; 440,505 Attorney, Agent, or Firm-Biebel, French & Bugg Related LS. Application Data [63] 583523;? of May 1972 Method and apparatus for scanning lumber, particularly cants, for determining the configuration thereof [52] Us Cl 250/561, 14432, 250/223 includes first and second light sources for directing [51] 60'1" 21/30 beams of light at a low angle of incidence across the [58] Field 250/223 cant. The light reflected from the cant at a plurality of locations provides information on the amount and ori- 250/560 356/199 209/] 1 L7 entation of useable wood within the cam. This infor- [56] References cued mation may be used to orient the cant prior to sawing into studs. By proper orientation and positioning of UNITED STATES PATENTS the cant relative to the saws, maximum yield from 2,828 9l7 4/1958 Wheeler 250/219 LG each cant may be realized 2,978,943 4/1968 Balint 250/2l9 LG 3,513,321 5/1970 Sherman 2091111.? 1 a m 8 Dr ng F gures a? 11 as 4 r 142 50 INTERFACE ELECTRONICS CHI ADJUSTMENT COMPUTER PATENTEDJUN 17 ms COMPUTER ADJUSTMENT CANT CH l PPER CHIPPER PATENTEBJUN 1 7 1915 PATENTEDJUN 17 ms SHEET CONTROL CIRCUITRY AUTOMATIC EDGER SET WORKS METHOD AND APPARATUS RELATED APPLICATION This application is a continuation of application Ser. No. 251,809, filed May 9, I972, now abandoned.

BACKGROUND OF THE INVENTION In processing lumber. and particularly the manufacture of studs from log blocks, the logs are usually manually oriented prior to being fed through bandsaws which cut the log into cants of either two or four inch thicknesses. The cants are then moved to ganged edgers where they are further cut into studs, thereby yielding either 2 X 2,2 X 4, or 4 X 4 inch studs. The material which remains, either in the form of sawdust or chips, is of less monetary value than the studs, and therefore it becomes apparent that obtaining the maximum number of studs from a given log block will not only increase profitability, but will also maximize the utilization of natural resources.

SUMMARY OF THE INVENTION This invention relates to a method and apparatus for scanning lumber, particularly cants, and orienting the cants with respect to saws to obtain therefrom the most useful and profitable material and to minimize waste of natural resources.

More particularly, this invention includes an optical scanner in which a first beam of light is directed at a low angle of incidence across the cant to illuminate the sawn portion and trailing wane and at the same time place the leading wane in shadow. A second beam of light is directed across the cant, also at a low angle of incidence, to illuminate the sawn portion and the leading wane, with the trailing wane being placed in shadow. The first and second light sources may be operated continuously, in which case an optical barrier will be used to prevent both the leading and trailing wanes from being illuminated at the same time. In another embodiment, the first and second light sources are alternately switched on and off thereby allowing a single set of light detectors to be used to sense the light reflected from the cant at a plurality of locations in a direction transverse to its direction of movement.

In the preferred embodiment, a plurality of photodetectors are positioned directly above the cant to observe the light reflected therefrom as the cant is moved by a conveyor. A tachometer or other pulse producing means is attached to the conveyor to provide information regarding to the position of the cant relative to the detectors. The conveyor includes lugs which engage the leading edge of the cant thereby to provide a reference against which all measurements are made.

At each of the plurality of locations across the cam being observed by a photodetector, the leading and trailing edges of the cant will be determined along with the leading and trailing edges of the sawn portion of the cant. This information is processed by a computer which is adjusted to determine the proper orientation and position of the cant with respect to chippers and ganged edgers to obtain maximum yield from each cant.

The output of the computer adjusts the position of alignment means mounted in line with the lugs on the conveyor. These alignment means adjust both the orientation and lateral position of the cant with respect to a fixed chipper. An adjustable chipper is positioned by the computer to remove wood from the opposite edge of the cant, and the cant is then moved through the chippers and then into the ganged edgers.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a plan view of a stud mill in which the method and apparatus of this invention may be utilized;

FIG. 2 is a perspective view of a portion of a log block and the location of saw cuts which may be made to produce a plurality of cants;

FIG. 3 is a diagrammatic illustration of a cam scanning station showing first and second light sources and a plurality of photodetectors for sensing the light re flected from a cant as it is moved by a conveyor, and also an electrical block diagram of a control circuit for orientating the cant and adjusting the cant chippers;

FIG. 4 is an elevational view of one embodiment of a cant scanning device constructed according to this invention;

FIG. 5 is a plan view of the cant scanning device of FIG. 4;

FIG. 6 is a detailed view of the scanning section of the cant scanner of FIG. 4; and

FIG. 7 shows the measurements made by the cant scanning device of FIGS. 36 with respect to a reference line.

FIG. 8 is an elevational view showing another embodiment of the invention where a single set of photodetectors is used and the light sources are alterna ei switched on and off.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and particularly to FIG. I, a stud mill is shown into which logs II) are moved by means of a conveyor 12 onto V-blocks l3 and then past an optical scanner 15 where log diameter is measured at a plurality of positions throughout its length. If the logs are not of acceptable quality, they are carried by conveyors l7 and 18 to the exterior of the mill. If the logs are of acceptable quality, they are received by a carriage mechanism 20.

The logs 10 may be rotated manually in order to present the optimum profile prior to scanning by an optical scanning device IS. The output of the optical scanner I5 is applied to circuit means, such as a properly programmed general purpose computer, which takes this information and determines the maximum number of studs which may be cut from the log. The computer therefore takes into consideration the fact that the log will first be cut into cants of either two or four inch thickness. In the embodiment shown, the center cut will be four inches thick since the carriage 20 is in excess of two inches.

The logs I0 are then moved to the right, as viewed in FIG. 1, between slab chippers 22 and 23, both of which are adjustable relative to the carriage 20 under the direction of the computer. These slab chippers will form faces 24 and 25, respectively, on the log 10, as shown in FIG. 2.

The log is then carried by the carriage 20 through adjustably positionable bandsaws 28 and 29 which will make cuts 31 and 32, respectively, in the log to form cants which then separate themselves from the log and are carried are conveyors 33 and 34 to pans 35 and 36. Whether the cuts 31 and 32 are made two or four inches from the surfaces 24 and 25 will be determined by the computer in order to yield the maximum number of studs of acceptable width and length from any given log.

The bandsaws 28 and 29 are then repositioned under the direction of the computer, and the carriage then moves the log through the bandsaws in the opposite direction to form cuts 37 and 38. The resulting cants are then carried by transfer conveyors 40 and 41 to conveyors 42 and 43 and stored temporarily on pans 44 and 45. The saws are then repositioned again, and the entire cycle repeated until the entire log has been di vided into cants having either two or four inch thicknesses. As explained above, the center cant will typically be four inches due to the size of the carriage mechanism 20.

The cants stored on pans 35, 36, 44 and 45 are deposited onto a conveyor which moves each cant past a second optical scanner 55. This scanner provides information to a computer which controls the position of adjustable stops 56 and 57 to orient each cant with respect to cant chippers 58 and 59. In the embodiment shown, cant chipper 58 is fixed while chipper 59 is adjustable. These chippers remove the wane from the cant in such a way as to maximize the number of studs available therefrom.

The two inch cants are carried by conveyor 61 through a four inch gang edger 62 which divides the cam into 2 X 4s and deposits them onto an outfeed conveyor 65. The four inch cants are carried by conveyors 66 and 67 through either a two inch gang edger 68 or the four inch gang edger 62 and then onto the outfeed conveyor 65.

By using an optical device which measures the volume of each log entering the mill, and by careful selection of the widths of the cants into which each log is cut, and the orientation of each cant with respect to the saws which divide it into studs, the number of studs available from any given log is increased over that presently available in manually controlled mills.

The second optical scanner is shown in FIGS. 3-5 with a cant 70 approaching the scanning position. The scanner includes a first source of light 71 which is so positioned as to direct the light at a low angle of incidence across a cant 70. Each cant includes a sawn portion 73 (FIG. 7), a leading wane 74 and a trailing wane 75. The leading wane 74 is defined as that portion of the cant 70 between the leading edge of the sawn portion 73 and the leading edge 76 of the cant. Similarly, the trailing wane is defined as that portion of the cant between the trailing edge of the sawn portion and the trailing edge 77 of the cant. The first light source 71 therefore illuminates the sawn portion 73 as well as the trailing wane 75.

Each cam 70 is carried to the optical scanner by a conveyor 50 which moves the cant at a first rate of speed. Within the area of the optical scanner 55, however, the cant 70 engages lugs 80 and 81 which are moved by a second conveyor 85. The second conveyor is moved at a second or slower rate of speed and therefore the conveyor 50 will force the leading edge 76 of the cam into positive engagement with the lugs 80. As will be explained, these lugs provide a reference against which the locations of the leading and trailing edges of the cant and the leading and trailing edges of the sawn portion of the cant is measured. In the embodiment shown in FIG. 4, equally spaced lug pairs 80 are carried by the conveyor 85. The conveyor 85 is moved at the second rate of speed by a motor 86 with its speed measured by a shaft encoding device or tachometer genera tor 90.

The optical scanner 55 also includes a second light source 91 which directs light at a low angle of incidence across the cant to illuminate the sawn portion 73 and the leading wane 74. In the embodiment shown, a light screen or baffle 95 is provided to maintain these two light sources separate so that the cant is illuminated by only one light source at a time. It is also within the scope of this invention, however, to provide switch means which will alternately energize the light sources in which case there would be no need for such a light screen.

A plurality of spaced photodetectors are positioned to sense the light reflected by the cant from the light sources 71 and 91. This reflected light provides information on the location of the edges of the cant as well as the edges of the sawn portion and will enable appropriate electronic circuitry to determine the maximum number of studs which may be cut from the cant and to orient the cant with respect to chippers and saws to yield this result.

In the embodiment shown in FIGS. 3-5, two sets of photodetectors and are employed, each set including 27 individual photodetectors spaced substantially equally across the cant. The photodetector set 100 observes the light reflected by the cant from light source 71 while the photodetector set 105 detects the light reflected by the cant from light source 91. Located within the viewing area of each photodetector set are baffles 106 which function merely to prevent stray light from causing erroneous readings by the photodetectors. Additional screens 107 are provided, also to prevent stray light from being directed into the viewing area and cause erroneous indications.

By combining the outputs from the individual photodetectors of the sets 100 and 105 with the output of the tachometer 90, a rectilinear representation of the available wood in the cant may be gene rated. Since the leading edge 76 of the cant may not be reasonably straight, a reference coordinate 110 against which this information is referenced is established ahead of the cant by approximately 10 inches and is generated by a detector located below the conveyor which senses the passage of one of the lugs 80 carried by the conveyor 85. Of course, other means for establishing a reference may be employed, such as a photodetector sensing the passage of a cam just prior to its moving into the viewing area.

Referring now to FIGS. 6 and 7, a cant 70 is moved by the conveyor 85 past the first set of photodetectors 100 and since the sawn portion 73 and the trailing wane 75 are illuminated by light from the source 71, both of these surfaces will reflect light into the photodetectors. Therefore, each photodetector output will show an increase of light at the beginning of the sawn portion and will not show a significant decrease in the level of illumination until after the trailing edge 77 of the cant passes. A photodetector output is shown by waveform with an increase in light intensity representing the leading edge of the sawn portion occurring at Y1 and a decrease in light intensity, representing the trailing edge of the cant occurring at (3.

As the cant 70 moves past the photodetector set 105, a second output waveform will be developed. Since the cant is now illuminated by the light source 91, the sawn portion 73 and the leading wane 74 are illuminated and therefore the photodetector will sense light at the leading edge of the cant, identified in the waveform at Y0, and the light intensity will fall off at the trailing edge of the sawn portion, identified at Y2, since the trailing wane 75 will be in shadow.

In FIG. 7, the distances Y0, Y1, Y2 and Y3 are shown measured from the reference 110 which is established when one of the lugs 80 passes the detector 1 15. Although not shown in FIG. 7, it is understood that these Y" distances are established for each of twentyseven positions across the cant.

As mentioned previously, it is within the scope of the invention to provide a single set of photodetectors and to provide two light sources with means to switch alternately between the sources, thus eliminating the need for a light screen.

Referring to FIG. 8, a set of photodetectors 130 are positioned on a line extending transversely across the conveyor system 55. A first light source 131 is positioned to the right, as viewed in FIG. 8, to direct light at a low angle of incidence across the cant 70 to illuminate the sawn portion 73 and the trailing wane 75. Similarly, a second light source 132 is positioned at the left in FIG. 8, to direct light at a low angle of incidence across the cant to illuminate the sawn portion 73 and the leading wane 74.

Each light source 116, 117 may include a plurality of light emitting diodes (LED) arranged with one or more LEDs for each photodetector position across the cant. The LEDs within each light source 131 and 132 may be connected in series and driven from a common power supply. The light sources 131 and 132 may be energized alternately and the output from the photodetectors 130 sampled during the period of energization to determine the amount of reflected light under the direction of a control circuit 135. Alternately, the light sources 131 and 132 may be switched at the same repetition rate but out of phase, and the photodetectors sampled in synchronism with the phase of the light sources. The switching rate may be governed by the tachometer generator 90 in accordance with the speed of movement of the cant.

In FIG. 8 where light emitting diodes may be used, they would be positioned closer to the cant than the steady state quartz-line lamps 71 and 91 shown in FIG. 3 since the intensity of the light output from light emitting diodes at present is less than that of other conventional light sources. A cylindrical lens may be used to focus the light onto the cant.

Once the grid coordinates of the leading and trailing edges of the sawn portion and of the cant itself are determined, the cant may be so positioned so that the leading wane may be removed by a fixed chipper 58 and the trailing wane removed by an adjustable clipper 59. To orient the wane with respect to the fixed chipper, a pair of adjustable stops 56 and 57, which are substantially in line with the lugs 80 and 81, are adjusted by the output of an electronic circuit 140 (FIG. 3). The adjustable stops 56 and 57 are attached to and positioned by stacked cylinder devices 141 and 142. These devices are pneumatically actuated cylinders which move in a digital manner through preset distances under the control of the circuit 130. The precision to which these devices may adjust the stops 56 and 57 depends upon movement of the smallest cylinder within each stack. Since the adjustable stops 56 and 57 are in line with the lugs 80, undulations in the leading edge of the cant will not effect the orientation of the cant with respect to the chipper. It may be seen in FIG. 4 that the lugs 80 disengage from the cant after the cant has passed through the scanning area and therefore the cant will accelerate to the speed of the conveyor until it engages the adjustable stops 56 and 57.

The position of the adjustable chipper 59 is also determined by the circuit 140 and will remove all or a substantial part of the trailing wane after the cant has been transferred from the conveyor 50 onto the conveyor 61 (FIG. 1). The positioning mechanism for the adjustable chipper 58 in a preferred embodiment of the invention is a device manufactured by General Electric under the trademark Accupin.

It is also possible within the scope of this invention to provide other means for positioning the cant with respect to the chippers 58 and 59. For example, the lugs could be adjustable independently of each other in order to position the cant. Also, while the cant is shown moving transversely through the scanner, it could also move longitudinally through the scanner with other means provided to orient the cant with respect to the clippers.

Also located within the scanning area is a sensing device which determines whether the cants are two or four inches in thickness. Memory means are pro vided to follow the cant through the chippers and to cause the cant to be directed either to the two inch or the four inch gang edges 62 or 68, depending on the size of studs required.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. A method of scanning cants having leading and trailing wanes to obtain the maximum yield therefrom including the steps of directing a beam of light at an angle of incidence across said cant such that a sawn portion and the trailing wane are illuminated and the leading wane is placed in shadow,

directing a second beam of light across said cant at an angle of incidence such that said sawn portion and the leading wane are illuminated and the trailing wane is placed in shadow, and sensing the light reflected from said cant at a plurality of locations to provide information on the location of the leading and trailing edges of the cant and the leading and trailing edge of the sawn portion,

whereby the locations of the sawn portion of the cant and the leading and trailing edges of the cant are identified at said plurality of locations. 2. Apparatus for scanning a cant optically to provide information regarding the location of the leading and trailing edges of the cant and a sawn portion thereof comprising conveyor means including a pair of indexing lugs adapted to engage the leading edge of the cant,

means for directing a first source of light at an angle of incidence across a cant for illuminating the sawn portion thereof and the trailing wane,

means for directing a second source of light at an angle of incidence across said cant for illuminating the sawn portion thereof and the leading wane,

a plurality of photodetectors positioned to sense the location of the leading and trailing edges of the sawn portion and the leading and trailing edges of the cam at said plurality of locations by observing the light reflected from said first and second light sources, and

circuit means responsive to the outputs of said plurality of photodetectors for locating the leading and trailing edges of the cant and the leading and trailing edges of the sawn portion with respect to said lugs.

3. Apparatus of claim 2 wherein said plurality ofphotodetectors includes a first set positioned to receive light reflected by said cant from said first source thereby sensing the location of the leading edge of the sawn portion and the trailing edge of the cant, and a second set positioned to receive light reflected by said cant from said second source thereby sensing the location of the trailing edge of the sawn portion and the leading edge of the cant.

4. Apparatus of claim 3 further including a light screen positioned between said first and second sets of photodetectors to prevent the first and second sources from illuminating said cant and reflecting light into said second and first set of photodetectors, respectively.

5. Apparatus of claim 2 wherein said plurality of photodetectors are mounted in a line substantially perpendicular to the direction of movement of said cant, said apparatus further including means to energize said first and second sources of light alternatively.

6. Apparatus for scanning a cant optically to determine the location of the leading and trailing edges of the cant and the sawn portion thereon, comprising a first source of light for illuminating the sawn portion and the trailing wane of the cant.

a second source of light for illuminating the sawn portion and the leading wane of the cam,

a plurality of photodetectors positioned to sense the location of the leading and trailing edges of the sawn portion and the leading and trailing edges of the cant at a plurality of locations across the cant by observing light reflected from said first and second light sources.

means for causing relative movement of the cant with respect to said photodetectors, and

means for providing information regarding the position of the cant relative to said photodetectors.

7. A method of optically scanning cants having a sawn portion and leading and trailing wanes including the steps of directing a beam of light at an angle of incidence across said cant such that at least the trailing wane is illuminated and the leading wane is placed in shadow,

directing a second beam of light across said cant at an angle of incidence such that at least the leading wane is illuminated and the trailing wane is placed in shadow, and

sensing the light reflected from said cant whereby the location of the leading and trailing edges of the cant and the leading and trailing edge of the sawn portion may be determined.

8. A method of optically scanning cants having a sawn portion and leading and trailing wanes including the steps of directing a beam of light at an angle of incidence across said cant such that at least the trailing wane is illuminated and the leading wane is placed in shadow,

directing a second beam of light across said cant at an angle of incidence such that at least the leading wane is illuminated and the trailing wane is placed in shadow,

moving the cant with respect to a plurality of light sensing means positioned above the cant, and sensing the light reflected from said cant with respect to the position of the cant as it moves relative to the light sensing means whereby the location of the leading and trailing edges of the cant and the leading and trailing edge of the sawn portion may be determined.

9. Apparatus for optically scanning a cant having a sawn portion and leading and trailing wanes to provide information regarding the configuration thereof, said apparatus comprising means for directing a first source of light at an angle of incidence across a cant for illuminating at least the trailing wane,

means for directing a second source of light at an angle of incidence across said cant for illuminating at least the leading wane,

a plurality of photodetectors positioned to sense the location of the leading and trailing edges of the sawn portion and the leading and trailing edges of the cant at said plurality of locations by observing the light reflected by the cant from said first and second light sources, and

conveyor means for moving said cant relative to said photodetectors,

circuit means responsive to the outputs of said plurality of photodetectors for locating the leading and trailing edges of the cant and the leading and trailing edges of the sawn portion with respect to said conveyor means.

10. Apparatus of claim 9 wherein said conveyor means includes a pair of indexing lugs adapted to engage the leading edge of the cant to provide a reference against which the location of the leading and trailing edges of the cant and the leading and trailing edges of the sawn portion of the cant is measured.

11. The apparatus of claim 10 wherein said conveyor means further includes a tachometer generator to sense its rate of movement. 

1. A method of scanning cants having leading and trailing wanes to obtain the maximum yield therefrom including the steps of directing a beam of light at an angle of incidence across said cant such that a sawn portion and the trailing wane are illuminated and the leading wane is placed in shadow, directing a second beam of light across said cant at an angle of incidence such that said sawn portion and the leading wane are illuminated and the trailing wane is placed in shadow, and sensing the light reflected from said cant at a plurality of locations to provide information on the location of the leading and trailing edges of the cant and the leading and trailing edge of the sawn portion, whereby the locations of the sawn portion of the cant and the leading and trailing edges of the cant are identified at said plurality of locations.
 2. Apparatus for scanning a cant optically to provide information regarding the location of the leading and trailing edges of the cant and a sawn portion thereof comprising conveyor means including a pair of indexing lugs adapted to engage the leading edge of the cant, means for directing a first source of light at an angle of incidence across a cant for illuminating the sawn portion thereof and the trailing wane, means for directing a second source of light at an angle of incidence across said cant for illuminating the sawn portion thereof and the leading wane, a plurality of photodetectors positioned to sense the location of the leading and trailing edges of the sawn portion and the leading and trailing edges of the cant at said plurality of locations by observing the light reflected from said first and second light sources, and circuit means responsive to the outputs of said plurality of photodetectors for locating the leading and trailing edges of the cant and the leading and trailing edges of the sawn portion with respect to said lugs.
 3. Apparatus of claim 2 wherein said plurality of photodetectors includes a first set positioned to receive light reflected by said cant from said first source thereby sensing the location of the leading edge of the sawn portion and the trailing edge of the cant, and a second set positioned to receive light reflected by said cant from said second source thereby sensing the location of the trailing edge of the sawn portion and the leading edge of the cant.
 4. Apparatus of claim 3 further including a light screen positioned between said first and second sets of photodetectors to prevent the first and second sources from illuminating said cant and reflecting light into said second and first set of photodetectors, respectively.
 5. Apparatus of claim 2 wherein said plurality of photodetectors are mounted in a line substantially perpendicular to the direction of movement of said cant, said apparatus further including means to energize said first and second sources of light alternatively.
 6. Apparatus for scanning a cant optically to determine the location of the leading and trailing edges of the cant and the sawn portion thereon, comprising a first source of light for illuminating the sawn portion and the trailing wane of the cant, a second source of light for illuminating the sawn portion and the leading wane of the cant, a plurality of photodetectors positioned to sense the location of the leading and trailing edges of the sawn portion and the leading and trailing edges of the cant at a plurality of locations across the cant by observing light reflected from said first and second light sources, means for causing relative movement of the cant with respect to said photodetectors, and means for providing information regarding the position of the cant relative to said photodetectors.
 7. A method of optically scanning cants having a sawn portion and leading and trailing wanes including the steps of directing a beam of light at an angle of incidence across said cant such that at least the traIling wane is illuminated and the leading wane is placed in shadow, directing a second beam of light across said cant at an angle of incidence such that at least the leading wane is illuminated and the trailing wane is placed in shadow, and sensing the light reflected from said cant whereby the location of the leading and trailing edges of the cant and the leading and trailing edge of the sawn portion may be determined.
 8. A method of optically scanning cants having a sawn portion and leading and trailing wanes including the steps of directing a beam of light at an angle of incidence across said cant such that at least the trailing wane is illuminated and the leading wane is placed in shadow, directing a second beam of light across said cant at an angle of incidence such that at least the leading wane is illuminated and the trailing wane is placed in shadow, moving the cant with respect to a plurality of light sensing means positioned above the cant, and sensing the light reflected from said cant with respect to the position of the cant as it moves relative to the light sensing means whereby the location of the leading and trailing edges of the cant and the leading and trailing edge of the sawn portion may be determined.
 9. Apparatus for optically scanning a cant having a sawn portion and leading and trailing wanes to provide information regarding the configuration thereof, said apparatus comprising means for directing a first source of light at an angle of incidence across a cant for illuminating at least the trailing wane, means for directing a second source of light at an angle of incidence across said cant for illuminating at least the leading wane, a plurality of photodetectors positioned to sense the location of the leading and trailing edges of the sawn portion and the leading and trailing edges of the cant at said plurality of locations by observing the light reflected by the cant from said first and second light sources, and conveyor means for moving said cant relative to said photodetectors, circuit means responsive to the outputs of said plurality of photodetectors for locating the leading and trailing edges of the cant and the leading and trailing edges of the sawn portion with respect to said conveyor means.
 10. Apparatus of claim 9 wherein said conveyor means includes a pair of indexing lugs adapted to engage the leading edge of the cant to provide a reference against which the location of the leading and trailing edges of the cant and the leading and trailing edges of the sawn portion of the cant is measured.
 11. The apparatus of claim 10 wherein said conveyor means further includes a tachometer generator to sense its rate of movement. 